title: Real-time motion and B0 corrected single voxel spectroscopy using volumetric navigators.
abstract: In population groups where head pose cannot be assumed to be constant during a magnetic resonance spectroscopy examination or in difficult-to-shim regions of the brain, real-time volume of interest, frequency, and shim optimization may be necessary. We investigate the effect of pose change on the B0 homogeneity of a (2 cm)3 volume and observe typical first-order shim changes of 1 μT/m per 1° rotation (chin down to up) in four different volumes of interest in a single volunteer. An echo planar imaging volume navigator was constructed to measure and apply in real-time within each pulse repetition time: volume of interest positioning, frequency adjustment, and first-order shim adjustment. This volume navigator is demonstrated in six healthy volunteers and achieved a mean linewidth of 4.4 Hz, similar to that obtained by manual shim adjustment of 4.9 Hz. Furthermore, this linewidth is maintained by the volume navigator at 4.9 Hz in the presence of pose change. By comparison, a mean linewidth of 7.5 Hz was observed, when no correction was applied.
authors.affiliation: Department of Human Biology, MRC/UCT Medical Imaging Research Unit, University of Cape Town, South Africa. aaron.hess@gmail.com
authors.forename: Aaron T
authors.initials: AT
authors.lastname: Hess
authors.forename: M Dylan
authors.initials: MD
authors.lastname: Tisdall
authors.forename: Ovidiu C
authors.initials: OC
authors.lastname: Andronesi
authors.forename: Ernesta M
authors.initials: EM
authors.lastname: Meintjes
authors.forename: André J W
authors.initials: AJ
authors.lastname: van der Kouwe
mesh_terms: D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology / Q000378:metabolism*; D003199:Computer Systems; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014018:Tissue Distribution